Valsartan, N-(1-oxopentyl)-N-[[2′-(1H-tetrazol-5-yl)[1,1′-biphenyl]-4-yl]methyl]-L-valine, is a known anti-hypertensive agent having the following formula (I):

Valsartan and its preparation are disclosed in U.S. Pat. No. 5,399,578, in particular in Example 16. One of the synthetic routes according to U.S. Pat. No. 5,399,578 can be schematically represented as follows:

The synthetic pathway comprises various steps, among which:                coupling of compound (3) with 2-chlorobenzonitrile to obtain compound (4),        radicalic bromination of compound (4) to give compound (5),        transformation of the brominated derivative (5) into the respective aldehyde derivative (6),        reductive alkylation of compound (6) to obtain intermediate (8),        acylation of compound (8) to obtain intermediate (9),        conversion of the cyano group to the tetrazole group to afford intermediate (10),        deprotection of the carboxylic group by hydrogenolysis to obtain valsartan.        
The preparation of valsartan according to the scheme reported above is very complex and badly suited to the production on an industrial scale. The synthetic process involves, inter alia, the use of highly toxic compounds, such as tributyltin derivatives. It would therefore be highly desirable to provide an alternative, improved industrial process for the preparation of valsartan, which reduces costs and, preferably, avoids the conversion of the cyano group to tetrazole group in one of the last synthetic steps. This in particular would prevent the contamination of the resulting valsartan with tin or azide derivatives during the last reaction steps. Moreover, said process would be safer as the use of butyltin derivatives, which are known to be toxic, would be avoided.
It has now been found an alternative process for the preparation of valsartan which fulfils the above mentioned requirements.